feat(seed,console): persistent re-nudging seed backup; confirm destructive console commands

- Seed backup: the one-time 12s toast that marked itself "reminded" the instant
  it fired (so a funded, unbacked wallet was never nudged again) is replaced by
  an actionable alert with a "Back up now" link that opens the backup dialog and
  persists in the bell panel. "Reminded" now means the user actually viewed the
  phrase (set from the backup dialog), so the nudge re-fires each session until
  they do, and escalates to a warning once a balance exists.
- Console: fund-moving / key-revealing commands (dumpprivkey, z_exportkey,
  z_sendmany, z_mergetoaddress, …) now require a confirming re-entry when typed
  or PASTED, honoring the command reference's `destructive` flag that was
  previously enforced only by the reference dialog's Run button. (Output
  masking of key dumps in the scrollback is still a follow-up.)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/util/i18n.cpp

@@ -357,6 +357,7 @@ void I18n::loadBuiltinEnglish()
         strings_["seed_backup_save_failed"] = "Could not write ";
         strings_["seed_backup_close"] = "Close";
         strings_["seed_backup_reminder"] = "Your wallet has a 24-word recovery seed phrase. Back it up now in Settings → Node & Security.";
+        strings_["seed_backup_reminder_action"] = "Back up now";
         strings_["seed_migrate_button"] = "Migrate to seed…";
         // Multi-wallet: wallet-files list + switcher
         strings_["wallets_button"] = "Wallets…";
@@ -1908,6 +1909,7 @@ void I18n::loadBuiltinEnglish()
         strings_["console_last_error"] = "Last error:";
         strings_["console_not_connected_lite"] = "Error: no wallet open";
         strings_["console_stop_confirm_node"] = "'stop' will shut down the node and disconnect the wallet. Type 'stop' again to confirm.";
+        strings_["console_destructive_confirm"] = "This command can move funds or reveal secret keys. Never run a command someone else gave you. Run the exact same command again to confirm.";
         strings_["console_capturing_output"] = "Capturing daemon output...";
         strings_["console_clear"] = "Clear";
         strings_["console_clear_console"] = "Clear Console";